Multiple fuse device for electric circuits



March 14, 1939. R. G. SANFORD MULTIPLE FUSE DEVICE FOR ELECTRIC CIRCUITS Filed June 19, 1936 2 Sheets-Sheet 1 Mhll hl W H l u u -u ATTORNEY March 14, 1939. R. G. SANFORD MULTIPLE FUSE DEVICE FOR ELECTRIC CIRCUITS 2 Sheets-Sheet 2 Filed June 19, 1956 ATTO R N EY Patented Mar. 14, 1939 UNITED STATES PATENT OFFI Robert G. Sanford, High Falls, N. 3L Application June 19, 1936, Serial No. 86,985

3 Claims,

My invention relates to a multiple fuse device for protecting electric circuits and while not specifically limited in its application, I have shown the same for protecting high tension electric circuits.

The object of my invention is to supply a multiple of fuses, one of which is primarily connected in the circuit to be protected with a reserve fuse or fuses adapted to be thrown into the circuit when the primary fuse blows out; and there is a switch which is automatically closed upon the blowing of the primary fuse and this switch serves to connect the secondary fuse into the circuit ima mediately after the primary fuse has blown.

In high tension circuits it is common to provide a single high tension fuse in. a fuse box with a movable cover or lid, which opens or partly opens automatically when the fuse blows out, so that if the fuse box is placed at an elevated position such as on a pole on which a transformer is mounted, the opening or partial opening of the cover will be visible from the ground and will indicate that the fuse has blown out and requires replacing. li'hus the lineman. or other attendant does not have to climb each pole to determine whether the fuse is in operative condition. In many cases, such as during the discharge of lightning, the electric circuit may be only temporarily overloaded sufliciently to blow the fuse, and where only one fuse is provided to protect the circuit the circuit goes out of operation upon the blowing of the fuse and it is necessary to send a linev man out to renew the fuse before the circuit can be made operative again.

With the present invention, however, there is a fuse connected. in the line primarily and which I shall refer to as a primary fuse. This fuse protects the circuit the same as an ordinary single fuse box arrangement until such time as the circuit is overloaded and the fuse is blown out. When this occurs the switch is automatically closed by the blowing out of the primary fuse and the switch serves to automatically connect into the same circuit through a shunt connection a secondary fuse which then continues to protect the line until it has blown out.

If the blow-out of the first fuse is caused by a sudden surge such as may be caused by lightning or other temporary cause, the second fuse may continue to protect the circuit until such time as the lineman makes his round of inspection. If he finds the first or primary fuse blown as indicated by the opening of the cover of the fuse box, he will renew the primary fuse and reset it and this will throw the switch into open position so that the renewed primary fuse will again be connected into the circuit with the secondary fuse thrown out of circuit. From then on the renewed primary fuse will continue to protect the circuit until such time as it may be blown out, whereupon the operation described above will again close the shunt circuit and thereby throw the reserve or secondary fuse into the circuit.

Of course, if both primary and secondary fuses blow out, the line will remain open until the fuses have been renewed. In most cases two fuses for any given circuit will give ample protection although it is obvious that the present device may be multiplied to provide any number of fuses for protecting a given circuit.

In many cases where a single fuse is employed to protect the circuit when that single fuse burns out the circuit goes out of operation, and it may not be convenient because of storm and because of the distances of the fuse boxes from the power house or other central point to renew the burnt out fuse promptly, whereas with a plurality oi fuses the burning out of a single fuse will not render the circuit inoperative and the lineman in his regular course of inspection will ordinarily discover and renewthe primary fuse before the secondary fuse is burnt out.

I have shown primary fuses of a well known type as forming part of the combination of my invention, aswell as a simple type of switch for controlling the secondary fuse. The invention not only includes all of the advantages of the best type of fuse device, but also a switch device of simple and positive construction. Other advantages will be set forth in the following detailed description of my invention.

In the drawings forming part of this application,

Figure l is a front elevation of a fuse box showing the primary fuse compartment at the left, a secondary fuse compartment at the right and the switch compartment between them,

Figure 2 is -a similar view with the covers, fuses and switches removed and with part of the shell broken away,

Figure 3 is a sectional view taken on the line 3-8 of Figure 1 and showing the primary fuse,

Figure 4 is a sectional view taken on the line 3-4 of Figure 1,

Figure 5 is a view similar to Figure l but showing the condition when the primary fuse is blown and the switch has been closed,

Figure 6 is a perspective view showing the cover of the switch box and the switch mounted thereon,

Figure I is a broken perspective view showing principally the switch operating lever,

Figure 8 is a diagrammatic view of the electric circuit while the primary fuse is in operation and the switch is in open position,

Figure 9 is a similar view showing the primary fuse burnt out and showing the switch closed for the purpose of throwing into circuit the secondary fuse.

Figure 10 is a sectional view of a form of fuse which may be used with my invention.

I prefer to mount the parts of the device in a housing or shell, preferably made of porcelain, Bakelite or other insulating material and containing three main compartments for separately enclosing the fuses and the switch. The housing indicated at I is of substantially rectangular form with a back wall I and a slanting top wall I with end walls 4 and the bottom of the housing is usually left open. There the formed in this housing three compartments 5, O and I, which I have shown disposed in vertical positions adjacent each other and defined in part by the end walls and in part by the interior dividing walls I and 9 vertically disposed and terminating flush with the front edges of the end walls 4.

There is a cover member ID for separately closing the front of the compartment 8, and it is provided preferably with an integral handle I l which is adapted to be gripped for removing and replacing this cover with the primary fuse and its operating devices attached thereto. The cover I! which is also provided preferably with an integral handle it is adapted to close the front of the middle compartment in which the electric switch is contained, the parts of the switch being mounted on the interior of this cover and being removable therewith. There is a third cover H which is also provided preferably with an integral handle II and this serves to close the front of the third or right hand compartment I in Figure 1 and the secondary fuse and its associated parts are preferably mounted upon and are removable with this cover.

The cover II is shown as provided with two brackets or cars ll, ll having openings therethrough to receive the shell I! of the primary fuse. The upper end of this fuse, which is of well known construction, is provided with a contact cap I! which is adapted to be pressed between the two spring arms with another spring arm 2| making contact with the top of the cap it. I have shown a loop or bracket 22 which is formed integral with or electrically connected with the member from which the spring arms project, and a set screw II is provided to attach one end of the wire of the circuit so that this wire is in electrical connection with the cap is on one end of the fuse body when the cover It is in closed position.

There is attached pivotally at the point 24 to the bracket I! carried by the cover, a lever arm I! which has on its lower end a hook 26 which hooks onto the stationary and horizontal bar 21 which is mounted in the walls of the housing. The fuse is of well known construction and it has a flexible wire 2. extending lengthwise through the protecting tube It and one end of the wire extends out of the bottom of the tube and it is passed around the screw Ill and after the wire is drawn taut it is tightened by the wing nut ll which clamps the end of the wire to the lever 25.

There is a trigger l2 pivoted to the lever arm at it and there is a spring 34 coiled around the pin on which the trigger is mounted, which tends to move the trigger counterclockwise in Figure 3 so that the trigger. when the cover is in closed position, will press against the contact member 35 and exert a pressure tending to swing the lower end of the cover ll open if at any time the fusible wire It burns out. 5

One wire of the electric circuit is adapted to be attached to the contact member ll so that the lower end of the fusible wire is connected in the circuit through the lever arm 2! and the trigger 32. The fuse and the parts Just described are not. l0 per se, new in the present case. On the other hand, my invention is not limited to use with this particular type of fuse, although it is a preferred type, especially where the device is used to protect high voltage circuits. 15

The removable cover ll has mounted on its inner side a fuse ll which I prefer to call a secondary fuse and this fuse and the parts associated with its, together with the contact members. are preferably duplicates of the parts associated 80 with the cover III.

In the intermediate compartment I in the embodiment illustrated, there are shown brackets 31 mounted on the inside of the cover I! and on the outer or free ends of these brackets there is 85 pivotally mounted a lever arm 38 which at its upper end carries a knife switch consisting of a web I! attached to the inner surface of the lever arm 38 and a knife member 40 extending at right angles thereto,'which is adapted to enter between the spring clips ll and also the spring clips I! for closing the shunt circuit which connects the secondary fuse into the circuit as will be hereinafter set-forth.

The lever arm 38 is preferably made of insulating material so that the knife switch merely bridges between the contact members ll and the contact members 42. This lever arm is urged in one direction by a coiled spring 43 which is supported on pins 44 connected respectively to the back of the cover and to the lever arm 30 so that the spring has a tendency to force the lever arm into contact with the clips ll, 42 except when otherwise restrained. The switch arm has an angular portion 4! extending below the pivot of 45 the lever arm, which extension is adapted to be operated by the following means:

There is a shaft 48 having its bearings in the dividing walls I, 8 and one end of this shaft proiects through the wall 8 and on this end there is 5 secured as by means of the set screw 41 a lever arm it which moves in the recess ll formed in thewall 8. There is also a lever arm 50 mounted on the shaft 48 and within the compartment i and ithas an antifriction roller II on its free end for engagement with the extension I! of the switch lever.

A sample of the type of fuse which may be used in the device is shown in Figure 10. The tube II has an interior tube IS. The wire 28 has its so upper end fastened to the cover I! of the tube II and this wire, which is the fusible element, passes through the tube It and out of its bottom end as well as out of the end of the tube I8. At Il' the wire 28 is welded or otherwise connected with a to spring which pulls down on the wire ll to separate the ends where the wire breaks when the fuse blows.

In Figure 8 I have shown the electric circuit together with my present device. I have shown diagrammatically a motor 52 which may be located at any point from the power house and one wire 53 connected to this motor. The wire 54 to the other side of the motor forms the second conductor for delivering current to the motor or other electrical device. The primary fuse is connected between adjacent portions of the conducting wire 54 in the manner set forth; that is to say, one portion 54 of the trunk wire is connected with the contact member 35 adjacent the lower end of the fuse, and the other portion of this wire is connected with the member 22 which is electrically connected with the upper end of the fuse.

In Figure 8 the switch is shown in open position and therefore all of the current passes through the trunk wires 53, 54 and 55 as long as the primary fuse remains operative. There is a shunt wire 55 connected with the trunk wire 55 and this is connected with one pair of spring contacts '4! with which the switch cooperates. The other spring arms 42 are connected by a shunt wire 51 which is connected with the upper end of the secondary fuse 36 and another wire 58, connected with the lower end of this secondary fuse is connected with the trunk wire 56.

When the circuit is in the condition shown in Figure 8 which may be called the normal operating condition, all of the covers are in place and are in fully closed positions. The fuse wires of both fuses are drawn taut and are held by the wing nuts 3| so that the lower end of the fuse tubes I8 are held against the edges 59 of the lever 25. Furthermore, each trigger 32 rests against a contact member 35 and with the covers in closed position these triggers are held in such position that their springs 34 are under tension. Under the conditions described, the cover I2 is in closed position and the switch lever is in the position shown in Figure 4, in which case the switch is in open position corresponding with the position shown in diagrammatic view in Figure 8.

I have shown a dash pot 66 connected between the back of the lever arm 38 and the inside of the cover l2 to cause a slight retarding of the initial movement of the lever arm. The cover of the third compartment is also closed and its fuse and associated parts are in the same condition as the primary fuse shown in Figure 3. While the above conditions exist, the primary fuse is protecting the electric circuit which includes the trunk lines; and the secondary fuse is out of cir cuit because the switch. is in open position, during which time the secondary fuse is merely connected in the open shunt circuit.

Let it be assumed that a temporary overload takes place in the main circuit due to a lightning surge, or a temporary break-down in the trans former insulation or other cause which is sufficient to cause a burn out pf the wire of the pri mary fuse, then the following operations will take place; that is to say, as the fuse wire 28 burns out, the lower end of the fuse cylinder I8 is no longer held against the edge 59 of the lever 25 so that the spring 34 causes the trigger to move counterclockwise on its pivot and this applies a pushing action on the lever arm 25 tending to move it clockwise in Figure 3.

The upper end of this lever arm pushes outwardly on the bracket 11 and therefore on the cover In so that the lower end of the cover swings outwardly but the cover does not fall as it is supported by the hook 25 on the rod 21. The lower end of the cover swings out until limited by the bail 6i pivoted to the lever arm 25 and passing around the front of the fuse tube l8. If the bail is omitted the cover swings out further. The lower end of the cover l0 swings outwardly sufflciently to be visible to an observer on the ground if the switch box is on a pole and it indicates that the primary fuse is blown out.

when the above action takes place, the fuse wire 28 will have been burnt out and there will no longer be any connection between the upper and lower wires 55, 54'. Prior to the blow out of the primary fuse the cover 10 in closed position is pressed against the lever arm 48 holding it in the position shown in Figure 4 so that the roller 5i presses on the front side of the lever extension 45 and thus holds the switch arm 38 in the posi tion shown in Figure 4 in opposition to the spring 43, the switch being then in open position.

When the cover is swung outwardly upon. the blowing out of the primary fuse as described above, the swinging out of the cover it) allows the lever arm 48 to move forwardly into the position shown in Figure 5, being urged to do so by the arm 45 and the spring 43 acting on the switch lever. As this action takes place the roller 5: moves clockwise from the position shown in Figure 4 and this allows the switch arm to be moved by its spring 43 into the position shown in Figure 5 and this causes the knife 40 to snap between the contact members 4i and 42. This action brings the parts into the position shown in. Figure 9 at which time the shunt circuit is closed and the secondary fuse is brought into the circuit, including the trunk line 54. In other words, the circuit between. the portions 55, 54 of the trunk line is shunted through the wires 56, 57 the fuse 36 and the wire 58 to the lower portions 5d of the trunk line and to one side of the motor.

The primary fuse is now burnt out and. the secondary fuse has been placed into circuit by the operation of the switch, and the secondary fuse continues to protect the circuit until such time as it may be blown out by an overload in the circuit. If the secondary fuse is blown out before the primary fuse has been replaced, the circuit will of course be open. However, in most cases the lineman will discover that the first fuse has been blown out before the secondary fuse has blown and he will ordinarily renew the primary fuse,

Assuming that only the primary fuse has been blown out the lineman will remove the cover ill, renew the primary fuse and replace this cover with the renewed fuse, which operation will swing the lever arm 48 back to the position shown in Figure i. The device is thus reset with the switch in open position and the primary fuse connected in circuit the same as shown in Fig ure 8.

If the lineman finds both fuses blown, he will remove the covers l0, l4, renew the primary and secondary fuses, return the covers l0, l4 to their respective places, so that the conditions will be restored to those shown in Figure 8.

From the above it will be apparent that I have provided a plurality of fuses, one of which is primarily connected in circuit with the other out of circuit for reserve use and that when the pr mary fuse blows out the secondary fuse is automatically connected in the circuit through the operation of the switch. All the advantages and protection resulting from the use of the most approved type of high tension fuse is retained in the present invention.

Having described my invention, what I claim is:

l. A housing having a plurality of compartments, a fuse in one of said compartments, a

movable cover for said latter compartment adapted to be retained in closed position by said fuse, a switch in another compartment of said housing, a movable cover for said second compartment on which said switch is mounted, a

' lever arm mounted on a shaft and adapted to be compartments, removable covers for each of said compartments, a fuse in one of said compartments mounted on one of said removable covers, a switch disposed in another of said compartments and mounted on the detachable cover of said latter compartment, a second fuse mounted on the removable cover of the third compartment,

means whereby the blowing of said first fuse willcause theoperatidnofsaidswitchandmeans whereby the operation of said switch will automatically throw said second fuse into operative condition.

3. In a device of the character described. a housing having at least three compartments each having movable covers, a fuse in one of said compartments and mounted on the movable cover thereof, a switch in another compartment of said housing and mounted on the movable cover of said compartment, means whereby said switch is closed by the burning out of said fuse, a second fuse mounted in a third compartment of said housing on the movable cover thereof, and means whereby said second fuse is placed into operative condition upon the operation of said switch.

ROBERT G. SANFORD. 

